Thermocompression (TC) bonding is often used in the manufacturing of electronic components for joining external leads to integrated circuit substrates. TC bonds between two articles are generally reliable when optimum parameters of time, temperature and pressure between the two articles are used. Several attempts for determining lead frame bond failure modes of film integrated circuits from automatic pull testers use only visual examinations of the lead frame bond area. Such time consuming processes of visual inspection by means of low power optical microscopes cannot fully characterize the failure modes because conventional visual inspection cannot reveal a fine microstructure, and the observation of the surface shows only the debris remaining after the dynamic process has ceased. Thus, for two failure modes possessing a similar morphology, conventional visual inspection cannot differentiate one from the other. Furthermore, there can be wide variations in failure mode classification between different operators observing the same bonds, and misclassifications can occur when large numbers of bonds are being inspected and operator fatigue becomes a factor.
A known method combining acoustic emission (AE) data with automatic pull testers to determine failure modes of bonded articles is described in U.S. Pat. No. 4,232,558 issued on Nov. 11, 1980 to M. C. Jon and V. Palazzo and assigned to the assignee herein. Such a known method comprises the steps of monitoring the AE signals emanating from the bonded articles during a destructive test, developing a signal proportional to the manner of excursions of the AE signals above a predetermined threshold, and comparing the developed signal to empirically determined ranges of signals to determine the bond failure mode. Such a known method clearly overcomes the above-mentioned limitations and disadvantages of visual inspection. Although the just-described prior art technique operates satisfactorily for its intended purpose, i.e., as a method for determining bond failure modes wherein the subjective and often inaccurate visual inspection is substantially eliminated this method is based on the comparison of AE counts with empirically determined counts resulting in some scatter and overlap of data. The foregoing may lead to misclassifications of failure modes in regions of substantial overlap of AE counts. In other words, there exists a need for more accurately systematically and consistently determined the failure modes of bonded articles subjected to destructive testing.